1. Field of the Invention
The present invention relates to an image reconstructing apparatus to reproduce or reconstruct an image by illuminating a hologram or holographic stereogram with an illumination light, a hologram forming method in which a view transform suitable for a light source used in the image reconstructing apparatus to form a hologram to form a hologram, a hologram formed by the hologram forming method, and also to a hologram sheet including a sheet on which a hologram is attached and adapted to limit the direction of the hologram in relation to the light source of the image reconstructing apparatus.
2. Description of the Related Art
A holographic stereogram is produced by sequentially recording many images formed by sequentially photographing an object from different points of view, as rectangular or dot-like element holograms on a single hologram recording medium.
Referring now to FIG. 1, there is shown a conventional method for forming holographic stereogram. For example, to form a holographic stereogram having parallax information only in the horizontal direction, first an object 100 is photographed sequentially from different points of view to provide a sequence of parallax images 101 formed from a plurality of images having the parallax information in the horizontal direction. Then, images 102 in the sequence of parallax images 101 are sequentially recorded as rectangular element holograms in a hologram recording medium 103 so that the parallax images will be in succession in the horizontal direction. Thus, a holographic stereogram having the parallax information in the horizontal direction is provided.
In the holographic stereogram, the information of the plurality of images 102 obtained by sequentially photographing the object from different horizontal points of view are sequentially recorded as rectangular element holograms so that they are in succession in the horizontal direction. So, when the holographic stereogram is viewed by the viewer with his or her both eyes, different two-dimensional images will be incident upon the right and left eyes, respectively. Thus, the viewer will feel a parallax and a three-dimensional image will be reconstructed.
In the conventional hologram reconstructing apparatus, the illumination light source for reconstructing a three-dimensional image is provided spatially apart from a hologram. So, a wide space is required for reconstruction of a conventional hologram, and the geometric relation between the hologram and illumination light source has to be set to meet specified requirements to reconstruct the hologram under optimum condition. This is also true for a hologram stereogram consisting of a plurality of element holograms.
On the other hand, if the illumination light source and hologram are integral with each other, the geometric relation between the hologram and illumination light source is always constant so that the hologram can always be reconstructed under optimum conditions.
Referring now to FIG. 2, there is shown a hologram viewing stand (HOLOSPOT4511 by Chuuou Seiki) which was designed and manufactured based on the above concept and is currently commercially available. In FIG. 2, the hologram viewing stand is generally indicated with a reference 110. The hologram viewing stand 110 includes an illumination light source 111 and hologram holder 112. A hologram or holographic stereogram 113 held on the hologram holder 112 is illuminated with an illumination light emitted from the illumination light source 111. The hologram viewing stand 110 is designed such that the light from the illumination light source 110 can always be incident upon the hologram or holographic stereogram 113 at an optimum incident angle.
However, it is desirable that a hologram or holographic stereogram can freely be viewed everywhere, not in a limited place. Therefore, an image reconstructing apparatus for reconstructing a hologram or holographic stereogram is desired to be highly portable and easy to carry on.
However, the conventional hologram viewing stand 110 is of a large stationary type. As shown in FIG. 2, since the illumination light source 111 is projected from the apparatus body, the stand 110 itself is not easily portable.
Also, when the stationary-type hologram viewing stand 110 is carried on, the geometric relation between the light source 111 and hologram holder 112 may possibly be changed so that the hologram or holographic stereogram 113 held on the hologram holder 112 cannot be reconstructed under optimum conditions.
To overcome the above-mentioned drawbacks of the prior art, a hologram reconstructing apparatus has been proposed which is compact and highly portable and in which the hologram is illuminated with an illumination light at an optimum angle of incidence. For changing the angle of visibility with the illumination light source kept optimized in relation to the hologram, however, the hologram itself has to be tilted horizontally or vertically.
Also, when viewing a hologram with a portable light source, it is difficult to move the hologram while the light source kept at a proper angle in relation to the hologram. As the result, it is not possible to assure a high quality of the hologram viewing.
Accordingly, the present invention has an object to overcome the abovementioned drawbacks of the prior art by providing an image reconstructing apparatus permitting to view a hologram with a high accuracy.
The present invention has another object to provide a method for forming a hologram suitable for viewing with the above image reconstructing apparatus, and a hologram formed by this method.
The present invention has still another object to provide a hologram sheet permitting a high quality of hologram viewing with the above image reconstructing apparatus.
The above object can be attained by providing an image reconstructing apparatus for reconstructing a hologram image, including according to the present invention:
an apparatus body provided with a holder for holding a hologram; and
a moving light source movable while keeping a predetermined angle of incidence in relation to the hologram held on the holder.
Also the above object can be attained by providing a hologram forming method for forming a hologram by recording a plurality of element holograms on a hologram recording medium, wherein, according to the present invention:
based on the moving locus of a light source to illuminate a hologram with a light for reconstruction of the hologram, a view transform is done to convert data in a parallax image train composed of a plurality of images including parallax information to a new parallax image train on which the element holograms are based.
Also the above object can be attained by providing a hologram formed by recording a plurality of element holograms on a hologram recording medium, wherein according to the present invention, based on the locus of movement of a light source to illuminate a hologram with a light for reconstruction of the hologram, a view transform was made to convert data in a parallax image train composed of a plurality of images including parallax information to a new parallax image train on which the element holograms are based.
Also the above object can be attained by providing a hologram sheet having a hologram attached in a predetermined area thereof, arranged, according to the present invention, to limit the direction in which the hologram is placed in relation to the hologram reconstructing apparatus based on the incident direction of a light from a light source provided in the hologram reconstructing apparatus.